This invention relates to surveillance of telephone calls over a public communications link and is particularly concerned with providing assistance for such surveillance to law enforcement agencies. It particularly concerns surveillance of voice over IP (i.e., cable) networks.
Requirements for enabling surveillance of electronic communications have been enacted into public law (e.g., Public Law 103-414 enacted 10/25/94; CALEA Communications Assistance for Law Enforcement Act) reciting requirements for assuring law enforcement access to electronic communications. Such access is required to be in real time, have full time monitoring capabilities, simultaneous intercepts, and feature service descriptions. The requirements specifically include capacity requirements and function capability. It is incumbent upon communication carriers to provide such capability and capacity.
While initially limited in scope, at present, to certain communications technology it is almost assured that it will be extended to new technologies of communications.
With present technology monitoring is limited to one monitoring location which location is static. It would be desirable to permit monitoring of telephones by more than one monitoring location at the same time and to permit highly secure monitoring at each of such locations.
Secure monitoring of a target IP telephone may be obtained simultaneously at a plurality of monitoring stations by requiring authentication to be provided by each of the monitoring stations prior to granting access permission to monitor the call. A single request generates multiple duplicate calls to a plurality of different monitoring location, each of which must be authenticated. When the monitored call arrives at each of the multiple monitoring stations a password is used to achieve authentication permission. The password is entered at each monitoring station by a touchtone keypad that generates Dual Tone Multi-frequency (DTMF) signals (e.g., each signal is a combination of two tones at different frequencies) which is sent to an IP monitoring center which grants surveillance intercept permission.
The monitored call is muted when the monitor receiver is initially engaged until the operator provides real time authentication. This avoids a pick up by some unauthorized listener.
A monitoring station may be connected to a Public Switched Telephone Network (PSTN) system and hence unable to directly monitor the target IP phone. Such a request is handled through a PSTN Check Point (PSTN-CP) which accepts the DTMF and forwards it to the IP monitoring center for validation. After pickup the PSTN-CP mutes the call until entry of a password granting access to avoid pick up by an unauthorized person.